Carbon blacks-free sulfur-vulcanised electrically conductive rubber blends

ABSTRACT

A practical and environmentally-friendly method, i.e. the high temperature-mechanical mixing by using an internal mixing device and a two-roll open milling device is used to produce the carbon blacks-free electrically conductive sulfur-vulcanised rubber blends of solid poly(butadiene-co-acrylonitrile) and solid sulfonic acid doped polyaniline. The addition of sulfur vulcanization system does not affect the electrical properties of the vulcanised blends. All vulcanised blends prepared by using this method show useful electrical conductivities up to the order of 10 −2  S/cm, good tensile strengths up to 18.0 MPa and colorable with the addition of a whitening agent. As a result, they have good potential to be used for manufacturing any antistatic products, electrostatic discharge or dissipative products and electromagnetic or radio frequency interferences shielding products.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.12/760,239 filed on 14 Apr. 2010, now U.S. Pat. No. 8,470,210, whichclaims priority to Malaysian Application No. PI20092620 filed on 22 Jun.2009, the contents of each of which are incorporated herein, in theirentirety, by this reference.

FIELD OF INVENTION

The present invention relates to carbon blacks-free sulfur-vulcanisedelectrically conductive rubber blends prepared by using a practical andenvironmentally friendly method, i.e. the high temperature-mechanicalmixing.

BACKGROUND OF INVENTION

As reported by U.S. Pat. No. 7,351,359 and Yong K. C. et al in hisjournal paper [European Polymer Journal, 2006], a non-practical andnon-environmentally friendly method, i.e. the solution mixing [involvedusing of large quantity of hazardous chemical solvents, e.g. chloroform,xylene, toluene and etc, in order to dilute bothpoly(butadiene-co-acrylonitrile) and sulfonic acid doped polyaniline]had been used to prepare this type of non-vulcanised electricallyconductive rubber blends. This was due to the great difficulty of directdispersing of solid sulfonic acid doped polyaniline within the solidpoly(butadiene-co-acrylonitrile) host matrix. Therefore, a morepractical and environmentally friendly method (with a quicker mixingperiod and without using any hazardous chemical solvents) needs to beintroduced for the purpose of preparing this type of sulfur-vulcanisedelectrically conductive rubber blends. Apart from this, a type ofchemical additive is also needed here in order to allow the directdispersion and to enhance the dispersing level of solid sulfonic aciddoped polyaniline within the solid poly(butadiene-co-acrylonitrile) hostmatrix.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a solid sulfonic acid dopedpolyaniline electrically conductive filler with protonation level ofbetween 40 to 100%, the filler is synthesised using aniline monomer witha purity level of 99±2 weight %, oxidant with a purity level of 99±2weight %, first doping agent with a purity level of 36 to 38 weight %,catalyst with a purity level of 99±2 weight %, dedoping agent with apurity level of 30 to 34 weight % and second doping agent with a puritylevel of 68 to 72 weight %.

Furthermore, the present invention also provides an electricallyconductive sulfur-vulcanised rubber blend, the blend contains 50.0 to99.0 p.p.h.r. of solid poly(butadiene-co-acrylonitrile) with 17 to 54weight % of acrylonitrile contents, 1.0 to 50.0 p.p.h.r, of solidsulfonic acid doped polyaniline electrically conductive filler withprotonation level of 40-100%, dispersing agent of solid sulfonic aciddoped polyaniline electrically conductive filler (which has beenprepared and premixed with 60 to 80 weight % of zinc oxide and 20 to 40weight % of dopant) with 2 to 4 times total weight % of the totalcontent of solid sulfonic acid doped polyaniline electrically conductivefiller, 0.5±0.05 p.p.h.r. of an antioxidant with a purity level of95-100 wt %, 0.5±0.05 p.p.h.r. of sulfur with a purity level of 95-100wt %, 3.5±0.1 p.p.h.r. of sulfur vulcanisation system's accelerator witha purity level of 95-100 wt %, 7.0±0.4 p.p.h.r. of sulfur vulcanisationsystem's activator with a purity level of 95-100 wt % and 1.0 to 5.0p.p.h.r. of a whitening agent with a purity level of 90-100 wt %.

Finally, the present invention also provides a process for preparingsulfur-vulcanised electrically conductivepoly(butadiene-co-acrylonitrile)-sulfonic acid doped polyaniline blends,the process includes a high temperature-mechanical mixing by using aninternal mixing device at a temperature of between 120 to 230° C., fillfactor of between 0.60 to 0.80 and rotors speed of between 80-120 roundsper minute and a two-roll open milling device at a temperature ofbetween 30-120° C.

The present invention consists of several novel features and acombination of parts hereinafter fully described and illustrated in theaccompanying description and drawings, it being understood that variouschanges in the details may be made without departing from the scope ofthe invention or sacrificing any of the advantages of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be fully understood from the detaileddescription given herein below and the accompanying drawings which aregiven by way of illustration only, and thus are not limitative of thepresent invention, wherein:

FIG. 1 illustrates the basic chemical structure of the smallest repeatunit of a sulfonic acid doped polyaniline example, i.e. the polyanilinedodecylbenzenesulfonate;

FIG. 2 illustrates the preferable example of the molecular chemicalstructure of poly(butadiene-co-acrylonitrile);

FIG. 3 illustrates the general 2-dimensional anatomical view of the mainstructures for a two-roll open milling device;

FIG. 4 illustrates the general 2-dimensional anatomical view of the mainstructures for an internal mixing device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to carbon blacks-free sulfur-vulcanisedelectrically conductive rubber blends. Hereinafter, this specificationwill describe the present invention according to the preferredembodiments of the present invention. However, it is to be understoodthat limiting the description to the preferred embodiments of theinvention is merely to facilitate discussion of the present inventionand it is envisioned that those skilled in the art may devise variousmodifications and equivalents without departing from the scope of theappended claims.

The present invention describes a practical and environmentally friendlymethod (i.e. the high temperature-mechanical mixing) on how to preparethe carbon blacks-free sulfur-vulcanised electrically conductive rubberblends. All sulfur-vulcanised electrically conductive rubber blends inthis present invention are based on poly(butadiene-co-acrylonitrile)[also known as nitrile rubber] as the rubber host and sulfonic aciddoped polyaniline as the only electrically conductive filler. These twomajor constituent polymers are known to be highly processable with thehelp of introduction of a special formulated dispersing agent for thesulfonic acid doped polyaniline filler in solid form. Allsulfur-vulcanised electrically conductive rubber blends in this presentinvention are also colourable with the inclusion of whitening agents.

In view of the great difficulty of direct dispersing of solid sulfonicacid doped polyaniline within the solid poly(butadiene-co-acrylonitrile)host matrix, it is now able to demostrate that the very highconductivities of the sulfur-vulcanisedpoly(butadiene-co-acrylonitrile)-sulfonic acid doped polyaniline blends(reaching at the order of 10⁻² S/cm) can be produced by using the hightemperature-mechanical method (i.e. with an internal mixing device and atwo-roll open milling device), which is a much more practical andenvironmentally friendly method if compared to the prior utilisedsolution mixing method. A special formulated dispersing agent is alsointroduced to the materials in order to enhance the processability anddispersion level of the solid sulfonic acid doped polyaniline within thesolid poly(butadiene-co-acrylonitrile) host matrixs.

This type of sulfur-vulcanised electrically conductive rubber blend isalso obtained from a carbon blacks-free formulation. In other words, itcan help to promote a cleaner and healthier (non-black)production/working environment. Potential commercial applications (suchas for antistatic products, electrostatic dissipating or dischargingproducts and electromagnetic or radio frequency interferences shieldingproducts) with more interesting visual appearance (i.e. the ability tobe incorporated with different colouring agents due to the inclusion ofwhitening agent into the rubber blend) can also be manufactured usingthis type of vulcanised rubber blend. Suitable methods for processingthis type of vulcanised rubber blend are including various types ofrubber processing equipment, such as injection moulding, extrusion andhot press-moulding.

Poly(butadiene-co-acrylonitrile)-sulfonic acid doped polyaniline blendmasterbatches with different compositions ofpoly(butadiene-co-acrylonitrile), sulfonic acid doped polyaniline, zinccompound and tetrakis-(methylene-(3,5-di-terbutyl-4-hydrocinnamate)methane are prepared by using a temperature controllable internal mixingdevice (at temperature 120-230° C., fill factor 0.60 to 0.80 and rotorsspeed at 80-120 rounds per minute).

Sulfur vulcanisation system agents, which including. sulfur, sulfurvulcanisation system's accelerator, and sulfur vulcanisation system'sactivator are added later to thepoly(butadiene-co-acrylonitrile)-sulfonic acid doped polyaniline blendmasterbatches by using a pre-warmed (at temperature 30-120° C.) two-rollopen milling device in order to avoid the premature vulcanisationproblem that can cause hardening and reducing the processability of theproduced blend masterbatches. Whitening agent is also added to each ofthe blend masterbatches by using the two-roll open milling device.

All sulfur-vulcanised poly(butadiene-co-acrylonitrile)-sulfonic aciddoped polyaniline blends [including 1 to 50 p.p.h.r. of solid sulfonicacid doped polyaniline electrically conductive fillers] prepared byusing the high temperature-mechanical mixing exhibit good electricalconductivities (with the range of order from 10⁻²-10⁻¹¹ S/cm) and goodtensile properties (with tensile strengths 6.0 to 18.0 MPa).

Mixing proportions and function of each of the main chemicals, rawmaterials and processing equipment that are used to produce thesulfur-vulcanised poly(butadiene-co-acrylonitrile)-sulfonic acid dopedpolyaniline blends are listed as following:

Aniline monomer (purity 99±2 wt %), antioxidant (purity 99±2 wt %),hydrochloric acid [HCl] solution (36-38 wt %, as the first dopingagent), anhydrous metallic chloride (purity 99±2 wt %, as the catalyst),ammonia solution (30-34 wt %, as the dedoping agent) and 68-72 wt % ofsulfonic acid solution (as the second doping agent) are used tosynthesis the solid sulfonic acid doped polyaniline with protonationlevel 40-100%.

1 to 50 p.p.h.r. of solid sulfonic acid doped polyaniline withprotonation level at 40-100% (as synthesised using procedures describedin the Example 1) are used as the only electrically conductive fillers.

From hereinbelow, the preferred embodiments of the present inventionwill be discussed in relation to the accompanying FIGS. 1 to 4, whichwill be used independently or in any combination thereof.

A special formulated (includes 60 to 80 weight % of zinc oxide and 20 to40 weight % of dopant, i.e. sulfonic acid) and premixed (with amechanical mixer, at temperature below 300° C.) dispersing agent isapplied here as the solid sulfonic acid doped polyaniline conductivefiller's dispersion agent. Its general compounding proportion is two tofour times of the total weight percentage of solid sulfonic acid dopedpolyaniline content for each blend.

50.0-99.0 p.p.h.r. of solid poly(butadiene-co-acrylonitrile), also knownas nitrile rubber [any grades with 17 to 54 weight % of acrylonitrilecontents] are used as the solid rubber host.

0.5±0.05 of sulfur, 3.5±0.1 p.p.h.r. of sulfur vulcanisation system'saccelerator and 7.0±0.4 sulfur vulcanisation system's activator [allwith purity, 95-100 wt %] are used as the ingredients of the sulfursystem vulcanisation purpose for all solidpoly(butadiene-co-acrylonitrile)-sulfonic acid doped polyaniline blends.

0.5±0.05 p.p.h.r. of antioxidant [purity 95-100 wt %] is included intoall blends in the hope to enhance their oxidation resistance.

1.0-5.0 p.p.h.r. of whitening agent [purity 90-100 wt %] are includedinto all solid poly(butadiene-co-acrylonitrile)-sulfonic acid dopedpolyaniline blends in order to bring out or enhance the colours of theblends when any types of colouring agent are included.

Two-roll open milling device is a general rubber processing device,which includes of main structures, i.e. a pair of counter-rotatingrollers in an open system and is equipped with a heating system in orderto control the rollers surfaces temperature. Size of the device isvaried and depends on the amount of material that is processed.

Internal mixing device is a general rubber or polymer processing device,which includes of some main structures in a closed system, i.e. acontrollable moving (up and down movements) ram, a pair of rotatingrotors (with controllable rotating speed) and equipped with a heatingsystem in order to control the mixing chamber's temperature. Size of thedevice is varied and depends on the amount of material that isprocessed.

Example 1 Preparation of 50±2 Grams of PolyanilineDodecylbenzenesulfonate (with Protonation Level, 48%) as theElectrically Conductive Filler in Dry Solid Form

Synthesis of Polyaniline-Emeraldine Base:

Hydrochloric acid [HCl] doped polyaniline is synthesised by oxidativechemical polymerisation. 50 mL of aniline (monomer, 99 wt %) isdissolved in 375 mL of 2 molar [M] HCl and pre-cooled to 1° C. Based onthe value of oxidant/monomer initial mole ratio (r) equal to 1.0, thesolution of oxidant is prepared by dissolving 125.2 g ammoniumpersulphate (99 wt %) with 276 mL of 2M HCl and pre-cooled to 1° C. Theoxidant solution is added gradually to the monomer solution over aperiod of 20±2 minutes, with constant stirring by an overhead stirrer toensure thorough mixing. The addition of oxidant can cause a suddenincrease in temperature. A few drops of anhydrous ferric chloridesolution (99 wt %) are added to the polymerisation mixture as acatalyst. The polymerisation mixture is maintained at temperature about0 to 2° C. with constant stirring in an ice bath, while the pH isadjusted to about 0 to 1 by adding a small amount of concentrated HCl.The mixture is left for 6 hours to complete the polymerisation. Themixture is then filtered and washed with 1500 mL of 2M HCl. The colourof the filtrate is reddish-pink due to the presence of soluble anilineoligomers. The mixture is washed with distilled water until the filtrateis colourless. To prepare polyaniline-emeraldine base, wet HCl dopedpolyaniline is deprotonated with a five times excess of ammonia (5000 mLof ammonia aqueous solution is prepared from 80 mL of 33 wt % ammonia)and is stirred for 24 hours. The resultant mixture is filtered and thenwashed with distilled water until the filtrate is colourless and noodour of ammonia can be detected. Wet polyaniline-emeraldine base islater washed with 750 mL of acetone [purity 99 wt %] for purification,before being finally dried in a vacuum oven (at 50° C.) until constantweight is obtained.

Doping of Polyaniline-Emeraldine Base:

Polyaniline dodecylbenzenesulfonate is prepared by protonating thepre-dried polyaniline-emeraldine base with aqueous solution ofdodecylbenzenesulfonic acid (70 weight % in 2-propanol) at a molar ratioof polyaniline-emeraldine base:dodecylbenzenesulfonic acid of 1:1 for 24hours under constant magnetic stirring. The resulted product [solidpolyaniline dodecylbenzenesulfonate, with protonation level at 48%] isfiltered and then washed with small quantities of distilled water. Theresulted product [solid polyaniline dodecylbenzenesulfonate, withprotonation level at 48%] is remained under suction by vacuum pump untilcracks are started to appear. A further 24 hours drying of the resultedproduct is carried out in a vacuum oven at 50° C. The dry solidpolyaniline dodecylbenzenesulfonate (with protonation level at 48%) haselectrical conductivity at 1.2±0.2 S/cm (as measured by using Van derPauw 4-probe method).

Example 2 Preparation of Sulfur Vulcanisation System ContainingPoly(Butadiene-Co-Acrylonitrile)-Polyaniline DodecylbenzenesulfonateBlend Masterbatches

Poly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonateblend masterbatches with different compositions [in parts per hundredrubber, p.p.h.r.] of poly(butadiene-co-acrylonitrile) [grade with 48weight % of acrylonitrile contents, with electrical conductivity in theorder of ×10⁻¹⁴ S/cm]: polyaniline dodecylbenzenesulfonate [withprotonation level, 48%, prepared as described in Example 1], i.e. 99:1,97.5:2.5, 95:5, 92.5:7.5, 90:10, 80:20, 70:30, 60:40 and 50:50 areprepared by using an internal mixing device as illustrated by FIG. 4. Afill factor of 0.70 (from the total free volume of an internal mixingdevice's mixing chamber) is used to perform all mixings. The startingtemperature for each mixing is 150° C. The rotor speed is 100 r.p.m.Stages of each mixing are as described in Table 1:

TABLE 1 Stages of Preparation of Sulfur Vulcanisation System ContainingPoly(butadiene-co-acrylonitrile)-Polyaniline DodecylbenzenesulfonateBlend Masterbatches by using An Internal Mixing Device Stage of mixingTiming 1. Addition of poly(butadiene-co- 0^(th) minute acrylonitrile) 2.Addition of polyaniline 1^(st) minute dodecylbenzenesulfonate anddispersing agent 3. Addition of tetrakis-methylene-(3,5-di- 3^(rd)minute terbutyl-4-hydrocinnamate) methane 4. Sweeping 4^(th) minute 5.Dumping 10^(th) minute (Total time = 10 minutes)

A special formulated dispersing agent (prepared with 60 weight % of zincoxide and 40 weight % of dodecylbenzenesulfonic acid; premixed in amechanical mixer at temperature 170° C.) is applied as the solidpolyaniline dodecylbenzenesulfonate conductive filler's dispersionagent. Its compounding proportion is three times of the total weightpercentage of solid polyaniline dodecylbenzenesulfonate conductivefiller's content for each blend. It is added to each of the blends byusing the internal mixing device (see FIG. 1) with procedures asdescribed by Table 1. 0.5 p.p.h.r. oftetrakis-methylene-(3,5-di-terbutyl-4-hydrocinnamate) methane (as theantioxidant) is also added to each of thepoly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonateblend masterbatches during the mixing (as described by Table 1). 4.0p.p.h.r. of titanium dioxide (as the whitening agent), 0.5 p.p.h.r ofsulfur, 3.5 p.p.h.r. of benzothiazole disulfide (as the vulcanisationsystem's accelerator), 5.0 p.p.h.r of zinc oxide and 2.0 p.p.h.r. ofstearic acid (both as the vulcanisation system's activators) are addedto each of the poly(butadiene-co-acrylonitrile)-polyanilinedodecylbenzenesulfonate blend masterbatches (with 1 to 50 p.p.h.r. ofpolyaniline dodecylbenzenesulfonate) on a pre-warmed (temperature at 50°C.) two-roll open milling device (with the nip's gap distance isadjusted to 2±0.2 mm). Each of the sulfur vulcanisation systemcontaining poly(butadiene-co-acrylonitrile)-polyanilinedodecylbenzenesulfonate blend masterbatches is then removed from thetwo-roll open milling device after 15 minutes of total mixing period.Prolonged mixing can cause premature vulcanisation due to the heatenergy generated through surface friction between the materials androllers.

Example 3 Preparation of Sulfur-VulcanisedPoly(Butadiene-Co-Acrylonitrile)-Polyaniline DodecylbenzenesulfonateBlends

Each of the sulfur vulcanisation system containingpoly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonateblend masterbatches as prepared on the two-roll open milling device (asdescribed in Example 2) is immediately used while it is still warm.Appropriate amounts (is varied with the targeted application) of each ofthe sulfur vulcanisation system containingpoly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonateblend masterbatches are cut and fed into a mould (dimension of the mouldis also varied with the type of targeted application). The mouldtogether with the sulfur vulcanisation system containingpoly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonateblend are sent for curing (with heating temperature 180±2° C. andduration based on the T_(c90) (curing time to at least 90% of curinglevel) of each blend (as measured by a Mooney's moving die typedrheometer) are reported in Table 2.

TABLE 2 T_(c90) (Curing Time to at least 90% of Curing Level) of SulfurVulcanisation System Containing Poly(butadiene-co-acrylonitrile)-Polyaniline Dodecylbenzenesulfonate Blends (Cured atTemperature, 180 ± 2° C.) Blend [poly(butadiene-co-acrylonitrile):polyaniline dodecylbenzenesulfonate] (p.p.h.r.) T_(c90) (±0.05 minute) 99:1.0 17.10 97.5:2.5  16.57  95:5.0 14.13 92.5:7.5  11.54 90:10 10.8780:20 10.37 70:30 10.25 60:40 10.14 50:50 10.02

Example 4 Electrical and Tensile Properties of the Sulfur-VulcanisedPoly(Butadiene-Co-Acrylonitrile)-Polyaniline DodecylbenzenesulfonateBlends

Sulfur-vulcanised poly(butadiene-co-acrylonitrile)-polyanilinedodecylbenzenesulfonate blends prepared by using the hightemperature-mechanical mixing (as described in Example 3) have theorders of electrical conductivity (measured using Van der Pauw 4-probesmethod) as summarised in Table 3, which rendered the material suitablefor various applications, such as for the electromagnetic or radiofrequency interferences shielding, electrostatic dissipative ordischarging and antistatic purposes.

TABLE 3 Orders of Electrical Conductivity (in the unit of S/cm) forSulfur-Vulcanised-Poly(butadiene-co-acrylonitrile)- PolyanilineDodecylbenzenesulfonate Blends Blend [poly(butadiene-co-acrylonitrile):polyaniline dodecylbenzenesulfonate] Electrical Conductivity (p.p.h.r.)Order (S/cm)  99:1.0  ×10⁻¹¹ 97.5:2.5   ×10⁻¹⁰  95:5.0 ×10⁻⁸ 92.5:7.5 ×10⁻⁷ 90:10 ×10⁻⁶ 80:20 ×10⁻⁴ 70:30 ×10⁻³ 60:40 ×10⁻² 50:50 ×10⁻²

Sulfur-vulcanised poly(butadiene-co-acrylonitrile)-polyanilinedodecylbenzenesulfonate blends prepared by using the hightemperature-mechanical mixing (as described in Example 3) also have somemain non-aged tensile properties (measured according to the standard,i.e. BS ISO 37-2005) as shown in Table 4.

TABLE 4 Non-Aged Tensile Properties of Sulfur-Vulcanised-Poly(butadiene-co-acrylonitrile)-Polyaniline Dodecylbenzenesulfonate Blends Blend[poly(butadiene-co- acrylonitrile):polyaniline Tensile Elongationdodecylbenzenesulfonate] (p.p.h.r.) Strength (MPa) at Break (%)  99:1.010.6 ± 0.5 790.3 ± 30.0 97.5:2.5  11.8 ± 0.5 720.9 ± 30.0  95:5.0 13.9 ±0.5 625.3 ± 30.0 92.5:7.5  17.1 ± 0.5 540.0 ± 30.0 90:10 14.1 ± 0.5342.8 ± 30.0 80:20 12.2 ± 0.5 273.7 ± 30.0 70:30 10.3 ± 0.5 200.5 ± 30.060:40  8.4 ± 0.5 125.3 ± 30.0 50:50  6.8 ± 0.5 102.5 ± 30.0

The invention claimed is:
 1. An electrically conductivesulfur-vulcanised rubber blend, the electrically conductivesulfur-vulcanised rubber blend comprising: 50.0 to 99.0-p.p.h.r. ofsolid poly(butadiene-co-acrylonitrile) with 17 to 54 weight % ofacrylonitrile contents; 1.0 to-50.0 p.p.h.r. of solid sulfonic aciddoped polyaniline electrically conductive filler with a protonationlevel of 40-100%; a dispersing agent of solid sulfonic acid dopedpolyaniline electrically conductive filler, which has been prepared andpremixed with 60 to 80 weight % of zinc oxide and 20 to 40 weight % ofdopant, with 2 to 4 times total weight % of the total content of thesolid sulfonic acid doped polyaniline electrically conductive filler;about 0.5 p.p.h.r. of an antioxidant with a purity level of 95-100 wt %;about 0.5 p.p.h.r. of sulfur with a purity level of 95-100 wt %; about3.5 p.p.h.r. of sulfur vulcanisation system's accelerator with a puritylevel of 95-100 wt %; about 7.0 p.p.h.r. of sulfur vulcanisationsystem's activator with a purity level of 95-100 wt %; and from about1.0 p.p.h.r. to about 20.0 p.p.h.r. of a whitening agent with a puritylevel of 90-100 wt %.
 2. The electrically conductive sulfur-vulcanisedrubber blend as claimed in claim 1, wherein the premix of 60 to 80weight % of zinc oxide and 20 to 40 weight % of sulfonic acid are usedas the dispersing agent of the solid sulfonic acid doped polyanilineelectrically conductive filler.
 3. The electrically conductivesulfur-vulcanised rubber blend as claimed in claim 2, wherein the premixof zinc oxide and sulfonic acid is prepared by using a mechanical mixerat a temperature below 300° C. and are used as the dispersing agent ofthe solid sulfonic acid doped polyaniline electrically conductivefiller.
 4. The electrically conductive sulfur-vulcanised rubber blend asclaimed in claim 1, exhibiting an electrical conductivity in a rangebetween 10⁻²-10⁻¹¹ S/cm and a tensile strength of between 6.0 to 18.0MPa.
 5. The electrically conductive sulfur-vulcanised rubber blend asclaimed in claim 1, wherein the electrically conductivesulfur-vulcanised rubber blend is colourable with an inclusion of awhitening agent with a purity level of 90-100 wt %.
 6. The electricallyconductive sulfur-vulcanised rubber blend as claimed in claim 1, whereinthe electrically conductive sulfur-vulcanised rubber blend is used tomanufacture products for antistatic, electrostatic discharge ordissipative and electromagnetic or radio frequency interferencesshielding purposes.
 7. A process for preparing the electricallyconductive sulfur-vulcanised rubber blend as claimed in claim 1, whereinthe process includes a high temperature-mechanical mixing by using aninternal mixing device at a temperature of between 120 to 230° C., fillfactor of between 0.60 to 0.80 and rotors speed of between 80-120 roundsper minute and a two-roll open milling device at a temperature ofbetween 30-120° C.
 8. The process as claimed in claim 7, wherein theblends exhibit electrical conductivities in the range of between10⁻²-10⁻¹¹ S/cm and tensile properties with tensile strengths of between6.0 to 18.0 MPa.
 9. The process as claimed in claim 7, wherein theelectrically conductive sulfur-vulcanised rubber blend are colourablewith an inclusion of a whitening agent with a purity level of 90-100 wt%.
 10. The process as claimed in claim 7, wherein the electricallyconductive sulfur-vulcanised rubber blend is used to manufactureproducts for antistatic, electrostatic discharge or dissipative andelectromagnetic or radio frequency interferences shielding purposes.